Chrome extension/app development

We have an online platform product, that we would like to develop a simple Chrome extension for. This extension would place a clickable link icon on the Chrome 'new tab' page showing our company's app icon - but this link needs to be user definable in the preferences, as each customer has their own subdomain which leads to their platform. 1) User downloads Chrome extension 2) User sets their subdomain in the extension settings panel 3) The extension appends this subdomain to form the complete link, and this can then be reached using the icon on the Chrome 'new tabs' page along with their other apps.